Spinal surgery involves many challenges as the long-term health and mobility of the patient often depends on the surgeon's technique and precision. One type of spinal surgery involves the removal of an existing intervertebral disc located between adjacent vertebral bodies. Procedures are known in which an existing intervertebral disc, for example, natural damaged disc tissue, is replaced with a disc prosthesis or with an interbody cage or fusion device. Replacement of a vertebral disc can include removing an existing intervertebral disc or portion of an intervertebral disc, distracting apart vertebral bodies, and inserting a replacement intervertebral disc into the intervertebral space.
This process can present the surgeon with several challenges. For example, the adjacent vertebral bodies typically collapse upon each other once the existing disc is removed. These vertebral bodies must be separated to an extent sufficient to enable the placement of the replacement intervertebral disc. However, if the vertebral bodies are separated, or distracted, beyond a certain degree, injury to the patient can occur.
There are several tools and techniques known for distracting apart vertebral bodies. One technique includes anchoring a pin in each of two adjacent vertebrae and imparting a force to the pins to distract the adjacent vertebrae. Typically, a pin is anchored into a vertebra by a surgeon who places the pin by hand based on landmark features of the vertebra bone and using heuristics gained from experience. In some instances, the surgeon can use fluoroscopy or x-ray to verify the position of the pin after the pin is anchored in the vertebra. Then, if necessary, the pin can be removed from the vertebra and the pin repositioned. Because the pins are typically positioned by hand and the final position and alignment of the pins can depend on the surgeon's skill, experience and technique, the pins are generally not consistently positioned nor typically is the alignment of a pin consistent with the alignment of the pin in the adjacent vertebra. In some instances, the procedure may include trial and error to gain a desired pin position and alignment.
There are also several tools and techniques known for inserting and aligning an intervertebral implant such as a prosthetic disc in an intervertebral space. Proper insertion and alignment of an intervertebral implant can be of great importance, but unfortunately, this process can be challenging interoperatively and the specific placement of implants can vary from one surgeon to the next.
A need exists for tools and methods for placing pins in vertebrae and for inserting and aligning intervertebral implants between vertebrae that overcome or minimize the above-referenced problems.